About this Author

College chemistry, 1983

The 2002 Model

After 10 years of blogging. . .

Derek Lowe, an Arkansan by birth, got his BA from Hendrix College and his PhD in organic chemistry from Duke before spending time in Germany on a Humboldt Fellowship on his post-doc. He's worked for several major pharmaceutical companies since 1989 on drug discovery projects against schizophrenia, Alzheimer's, diabetes, osteoporosis and other diseases.
To contact Derek email him directly: derekb.lowe@gmail.com
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March 16, 2011

Potassium Iodide Pills

Posted by Derek

Well, the nuclear crisis in Japan seems to be causing a run on potassium iodide (KI), and not just in Japan. If news reports are to be believed, people in many other regions (such as the west coast of the US and Canada) are stocking up, and some of these people may have already started dosing themselves.

Don't do that. Don't do it, for several reasons. First, as the chemists and biologists in this site's readership can tell you, it's not like KI is some sort of broad-spectrum anti-radiation pill. It can protect people against the effects of radioactive iodine-131, which is a major fission product from uranium. It does that by basically swamping out the radioactive iodine a person might have been exposed to, keeping it from being taken up into the body. Iodine tends to localize in the thyroid gland, and that uptake and local concentration is the real problem. An unfolded newspaper will shield you just fine from the alpha particles that I-131 gives off, but not if it's giving them off from inside your thyroid. Correction: I-131 is a beta/gamma emitter - my apologies! The point about not wanting it in your thyroid, of course, stands. . .

And this is why potassium iodide won't do a thing to help with the other radioactive isotopes found in nuclear reactors. That includes both the uranium and/or plutonium fuel, as well as the fission products like strontium-90 and radioactive cesium. Strontium-90 is a real problem, since it tends to concentrate in the bones (and teeth), and it has a much longer half-life than I-131. Unfortunately, calcium is so ubiquitous in the body that it's not feasible to do that uptake-blocking trick the way you can with iodide. The only effective way to deal with strontium-90 is to not get exposed to it.

Another good reason not to take KI pills is that unless you're actually being exposed to radioactive iodine, it's not going to do any good at all, and can actually do you harm. Pregnant women and people with thyroid problems, especially, should not go around gulping potassium iodide. Nothing radioactive is reaching North America yet - there's the Pacific Ocean to dilute things out along the way - which makes it very likely that more people on this side are in the process of injuring themselves by taking large unnecessary doses of iodide. This is like watching people swerve their cars off the road into the trees because they've heard that there's an accident fifty miles ahead.

Now, if I were in Japan and downwind of the Fukushima reactors, I would indeed be taking potassium iodide pills, and doing so while getting the hell out of the area. (That last part, when feasible, is the absolute best protection against radioactive exposure). But here in North America, we're already the hell out of the area. The only time to take KI pills is when a plume of radioactive iodine is on the way, and that's not the case over here. We'll have plenty of notice if anything like that happens, believe me - any event that dumps enough radioactivity to make it to California will be very noticeable indeed. Let's hope we don't see anything of the kind - and in the meantime, spare a thought for those reactor technicians who are trying to keep such things from happening. Those people, I hope, will eventually have statues raised to them.

I agree that those reactor workers are heroes, and I have been thinking about them these past few days.

Rather than statues, I was wondering if there could be a way to donate towards the future support of their families, specifically. While general donations are needed to help the thousands displaced, these folks are giving up so much more than money to protect those thousands and (perhaps) many many more. Heroes indeed.

You have me cringing a little, probably the same way you cringe when someone outside the drug industry tries to get technical about drugs.

I'm a retired nuclear engineer who was trained to operate the GE Mk I reactor (the Japanese type) by TVA. I spent 2 years after the '75 fire crawling all over the Unit 1 and 2 reactor systems at Browns Ferry nuclear plant (also a Mk I). I spent three years working the accident at Three Mile Island. My specialty is high range nuclear instrumentation and its calibration.

We're playing in my back yard now :-)

If I lived downwind of of the Japanese reactors I would NOT be dosing with KI. Why? Because there has been no release of I-131 that matters and there probably won't be.

What we found at TMI was that the radioiodine and radiocesium chemically combined to form the solid cesium iodide. This chemical dissolved in the water inside the containment where it stayed. So instead of the iodine being a volatile gas, it became a harmless (outside the containment) compound.

The wildly varying radiation readings on the ground around the plant tell me that they're measuring noble gas emissions. The isotopes of xenon and krypton. The problem is, these isotopes being gases, they get INSIDE the instruments and cause false high readings. The instruments are calibrated to measure radiation coming from outside the instrument.

That was a problem at TMI and it's a problem here. In designing radiation monitors capable of measuring the noble gas activity inside the reactor building, I ran into the same problem. The gases are heavy and settle out and they cling to things, especially polymers.

I don't have any special insider contacts anymore but from filtering through the horrendous mass media coverage and information from some industry sites, I haven't seen anything to be worried about. Yes, this is an unmitigated disaster to the utility company just like TMI was to GPU. But unless something almost inconceivable goes wrong in the next few days, the impact to the world outside the plant boundary will be nil.

particularly sobering is that the reactors are still generating 6-10 MW of decay heat, a huge amount of energy to dissipate.

and to quote the site:
"If the decay heat is not removed then the reactor fuel begins to heat up and undesirable consequences begin as the temperature rises such as rapid oxidation of the zircaloy cladding (~1200C), melting of the cladding (~1850C), and then the fuel (~2400-2860C)."

jgd (#6), I hadn't figured on iodine being released as elemental I2. The larger amount of cesium produced in the decay chain would seem to pretty much ensure that you're going to get a lot of cesium iodide, just on chemical reactivity considerations. Looks like there can be further chemistry after that, though (http://dx.doi.org/10.1016/1359-0197(88)90070-7).

Your point about the noble gases and their effects on detection is interesting. From what I read, though, the krypton isotopes involved all have half-lives of seconds to minutes. Xenon-135 is about 9 hours, though. The MIT site mentioned above (http://mitnse.com/) discusses release of these from the Fukushima reactors.

Do you have any comments about radon-222? It's apparently one of the main volatiles, with a half-life of a few days. That one's an alpha-emitter, though, and I haven't seen any discussion about what sorts of radiation is being detected near the reactors.

It is true that KI only protects the thyroid and will not protect against other radioactive elements that are produced and may be released by a nuclear power plant. However, authoritative peer reviewed studies documented at least a 100-fold increase in thyroid cancers in the former Soviet Union post-Chernobyl and no increased incidence in Poland where KI was distributed. The only other well documented health outcomes from Chernobyl were due to acute radiation exposure from the emergency response teams, the so-called liquidators, and widespread severe psychological impacts. The cases for leukemias and other genetic damage are much weaker. So to say KI protects the thyroid against one form of radiation is saying a lot, actually.

That said, you are absolutely right that people in North America should not be taking KI. But not because it's harmful. Of the 18 million people given KI in Poland post-Chernobyl there were exactly 2 serious adverse health reactions. And those two people had pre-existing iodine allergies. [Amer. J. Med (1993) 94, 524.] In addition to people with pre-existing thyroid conditions or iodine allergies, it's also not particularly helpful for people over the age of 40 years and caution is needed in dosing neonates. The real reason people in North America shouldn't take KI is because global supply is limited and we should save the KI for the Japanese who might actually need it.

"Those people*, I hope, will eventually have statues raised to them." [* the Fukushima nuclear workers]
-- My most earnest sentiments exactly.

@6 jgd
I'm a biologist (not a radiophysicist) but I did work as an undergrad in Boston with a group that radio-iodinated their own nucleotides to make 131-I-deoxyuridine -- used for non-invasive tracking of leukemic cell cell-population kinetics in mice. Anyway, this is by way of seconding your sentiments that for folks to be chowing down on KI tablets when, so far as I know, there's no evidence of major radioiodine plumes coming their way is pretty damn silly.

@ #7 CB - Just to clarify for the readers, the post at mitnse.com was not written by a nuclear engineer, but by someone who studies risk management in corporations (http://www.boingboing.net/2011/03/15/an-expert-in-one-fie.html).

TEPCO and the government of Japan may be spinning events to prevent fears from spreading more widely, but the experts on the ground - those "Fukushima 50" (now probably double that number) are clearly worried to the point that they are in all likelihood sacrificing their health, and perhaps their lives, to prevent further disaster. I am in awe of these people.

The local news in N CA are advising against taking KI, but the local drugstore is sold out - I checked when I was on an errand. Now that we have gotten over the boats being swamped on the coast here, the "radioactive plume" coming across the Pacific Ocean is the next big local news topic.

@12 SteveH: Actually if you read the Boing Boing post and the mitnse blog entry its very clear that the post originated with an MIT mechanical engineer but has now been edited and vetted by the nuclear science and engineering dept at MIT.

I vaguely remember that I was given a few mililiters of iodine-containing solution (I guess it was KI3, Lugol's iodine, because of the very dark color of that liquid) after the Chernobyl disaster (in Poland). I wonder why they didn't give us just KI. I remember rumours that some kids were even dosed with tincture of iodine (alcoholic solution of I2 and KI3).

In the grand old days when I was still in research there was a lot of iodination of proteins taking place in our NIH lab (and my boss was a thyroid endocrinologist who was very active in the Marshall Islands research efforts during the late 1950s early 1960s to understand the effects of the bomb testing on the citizens of that area; he also did a site visit to Chernobyl several years after the incident). It was common for those of us doing iodination experiments to place a drop of super-saturated KI on our tongue an hour before the experiment to block our thyroid in case there was a problem with containment of the experiment.

I remember the day that Three Mile Island blew. My boss and several others in the NIH branch were summoned downtown without being told why. When they got there they were asked point blank about whether KI should be distributed to the citizenry in the area. They noted it was probably too late if there was a containment breach but a good prophylactic if not.

As JGD notes in #6, there was no radioactive iodine from Three Mile Island. In fact the Kemeny report on the accident showed that there was some novel and unexpected nuclear chemistry that took place. What is going on in Japan is totally different as containment has been breached and there may be radioactive iodine released (this was the case in Chernobyl and there were a significant number of thyroid cancers as a result). The big problem will be if the prevailing winds blow over land depositing fall out on agricultural lands.

There are two major noble gases of interest at this point. The Xe-135 is just about gone. That leaves Xe-133 with a half life of 5.25 days and a rich spectrum of high energy gammas in addition to being a beta emitter.

In a week or so the other major noble gas Kr-85 with a 10.7 year half life. It is a minor gamma emitter (0.514meV, 0.4% yield) but an energetic beta emitter which makes it of concern if inhaled.

Radon-222 only has a half-life of 38 seconds and its fission yield is very low so whatever amount that was present at shutdown was gone in a few hours.

One of the things that has driven me crazy about the coverage is that no one will say what the radiation is, even if they don't know exactly what the elements involved are. I assume it's a mixture of everything, but it'd be nice to know roughly what the relative amounts are and if they can take a guess at the elements involved. I remember an old trivia question along the lines of:

You are given an alpha-emitter, a beta-emitter, a gamma-emitter, and a neutrino-emitter. (Bear with me a bit on this one.) You have to hold one in your hand, put one in your pocket, swallow one, and throw one away.

The answer is to hold the alpha-emitter, pocket the beta-emitter, throw away the gamma emitter, and swallow the neutrino-emitter.

Otherwise, I kinda wish I had thought ahead far enough to stock up on KI pills and sell them to other Americans with more money (and irrational fear) than sense.

I heard the nuclear cookies story with an alpha, beta, gamma and neutron emitter. Then the solution goes like this:

alpha emitter: put it in your pocket. the cloth is enough distance and shielding. just don't eat it
beta emitter: hold it in your hand. that kills most of the exposure
gamma emitter: eat it. that more than doubles your exposure from having it in your hand, but since you can't shield it like you can the beta emitter, might as well not even try
neutron emitter: very bad news. throw it as far away from you as you can

Regarding Three Mile Island, there was a shortage of pharmaceutical grade potassium iodide in the immediate aftermath. By the time a supply of super saturated KI solution was manufactured and transported to the area anyone exposed to radioiodines would have been out of luck. Fortunately this incident did not release radioiodines to the surrounding, but the near miss prompted one local man with a young daughter to start a company to manufacture KI pills in 1982. That company remains one of the major suppliers of KI today.

Rn-222 has a half-life of 3.8 days. It's not a fission product; it is produced by the natural decay of U-238.
I highly recommend the book "A Guidebook to Nuclear Reactors" by Anthony V. Nero, Jr. for anyone looking for a semitechnical introduction to nuclear reactors. I don't know if the book is still being published but a copy of a report that appears to be nearly identical can be downloaded free at www.osti.gov/bridge/purl.cover.jsp?purl=/7262735-PGJ6j7/. (This is quite old but the physics hasn't changed.)
The Japanese nuclear crisis is another example of the perils of scaling up (see "175 Times. And Then the Catastrophe.", Sept. 18, 2009). Large reactors require cooling after being shut down because they are large; small reactors don't. There has been some interest in smaller modular reactors; some designs wouldn't require shutdown cooling and would therefore be inherently safer.

The radiation spikes measured outside the plants are from nobel gases with short half-lives that tend to give anomalously high readings. Even if the plume was directed straight at Berkeley, a good share of the radioactivity would have decayed before arriving there.

I'll add:

There is negligible chance of a criticality accident at this point. Moderation has been lost and the control rods are fully inserted. If there's a meltdown, it will be of unmoderated fuel mingled with control rods.

And the point that really irritates me: The last estimate I heard was 25,000 dead. That may be pessimistic, but over 10,000 is not. None of these were killed by radiation. Indeed, I've heard no reports of anyone being so much as sickened by radiation. Some perspective, people.

There is negligible chance of a criticality accident at this point. Moderation has been lost and the control rods are fully inserted. If there's a meltdown, it will be of unmoderated fuel mingled with control rods.

They're talking about criticality in the spent fuel storage pools. There aren't any control rods in the pools. To make matters potentially worse, the pools aren't inside the heavy-duty containment vessels like the actual active reactor cores are.

I am not a nuclear engineer or a health physicist, but I'll share what I know.

Any radioactive material released by the reactors is going to produce all four kinds of radiation, but IIRC it will mostly be beta radiation.

Alpha is produced in the decay chain of uranium and other very heavy elements. It's greater in reactor fuel than in natural uranium because the reactor fuel is enriched with the shorter-lived U-235, and greater still after the fuel has been in a reactor due to the presence of some relatively short-lived transuranics. However, it's not the radiation of greatest concern.

Neutron radiation is produced by fuel recently removed from a reactor (and by "recently" I mean a few minutes ago.) It is produced as a byproduct of certain beta decays, which in turn are byproducts of fission. As you probably know, the heavier the isotope, the higher the proportion of neutrons required to stabilize it. So when a uranium atom fissions, the products tend to be very neutron-rich. When a very neutron-rich isotope beta decays, the energy release is sometimes enough to shake loose a neutron as well. However, such highly neutron-rich isotopes have very short half-lives, so this radiation disappears very quickly -- most is gone within seconds once the chain reaction stops. The longest half-life for a neutron emitter I could Google was 56 seconds. So this is really not going to be an important component of the radiation.

That leaves beta decays, which are an important component of the natural decay chains (there's roughly one beta per alpha decay) and the predominant component of fission product decays. I mentioned that fission products tend to be very neutron-rich; beta decay brings these products back into the "valley of stability." As you get closer to the vally of stability, neutron emission disappears, but the half-life increases, up to decades for some of the nasier contaminants such as strontium-90. These are the ones you worry about.

Gammas are a byproduct of other forms of decay. Alpha and beta decay sometime leave the daughter nucleus in an excited state, which deexcites by emitting a gamma. However, the longer-lived beta emitters, particularly strontium-90, tend to decay directly to the ground state and so produce few gammas.

Hope that helps.

I read a news report that some folks are painting their necks with Betadine. This makes about as much sense as trying to avoid diptheria by painting your neck with penicillin. Lots of hysteria out there. Concern is justified; hysteria is not.

The fuel in the cooling ponds is spent fuel, which is harder to drive to criticality. Also, if I'm not mistaken, the cooling water is not pressurized. Any significant heat generation is going to boil off the water and leave the spent fuel unmoderated. I'm not sure I understand the concern.

jgd- Your first comment is one of the most interesting things I've read on this disaster. (In fact, I am quoting it in a post on my own site.)

But you did leave me wondering just how wrong those readings might be. This may be unfair, but could you give us a rough estimate or even an informed guess? (From your discussion, I guessed that they might be as much as twice as high as they should be.)

Your post and these resultant comments have been more informative by several orders of magnitude than was the past week's media barrage. I am an alumnus of a couple military NBC detect/decon schools and served in battalion and regimental NBC billets back in the eighties. I still consider bio or chem a lot scarier than anything radiological, as far as non-state threats are concerned.

I called up our local preparedness retailer last Monday to inquire about their stock of potassium iodide pills. I was curious to see how Utahns were reacting to the situation. They were sold out, but stressed that they never kept a large inventory of that product anyway.

#20 @Jon, since they're quoting the dose rates in rem or sieverts, it doesn't matter what the specific emission is. By definition, those are absorbed dose, and computed by taking the dose (in Roentgen or Gray respectively) and multiplying it by an absorption factor. Gammas and betas have an absorption factor of 1, alpha of 20. Neutrons around 10 depending on energy if I recall correctly.

Anyway, the point is that a rem is a rem, no matter what the form of the radiation is.

@34 THANK YOU! Someone FINALLY mentions iodized salt. Apparently everyone has forgotten about this product that takes up at least two linear feet of shelf space in every grocery store across the country. Dustydog, according to the box of iodized salt that's been in my cupboard for over a year, the contents are less than 1% KI, but 1/4 teaspoon will provide 45% of your daily required iodine. So to every idiot out there that's looking for potassium iodide, just get yourself a box of iodized salt, put a teaspoon of it in a glass of warm water and drink it.

At the time of writing, popular news reports are citing the elevated levels of radiation found in goat's milk and spinach in Japan. I haven't been able to find the numbers (with background levels), but thought it was worth noting.

"[T]he experts on the ground ... are in all likelihood sacrificing their health, and perhaps their lives, to prevent further disaster."

While this impression is understandable, given the standard media reporting, it is also far from accurate.

The highest individual acute dose I've read of, 25 Rem, is certainly not insignificant, but may not even be high enough to produce any symptoms that could be distinguished from a cold. As for cumulative exposure, as a former Navy nuclear engineer it is my opinion that the long-term health risks associated with aerosol metals and other carcinogens in the smoke there outweigh any potential radiation effects.

I admire the heroism of those in Fukushima working to solve the problems caused by the tsunami. However, TEPCO and its contractors have shown truly irresponsible behavior. The incident involving hauling fissionable material in large buckets, which caused a horrible accident in which 2 of the 4 workers IIRC died from radiation poisoning. Attempts to cover up made by the contractor and municipal officials exposing the town to a relatively high level of radiation. The inability of Japanese journalists to report accurately (partly due to cultural mores) and the sensationalism aired by US media outlets are equally disappointing. Sho ga nai, ne - it can't be helped.

At the time of writing, popular news reports are citing the elevated levels of radiation found in goat's milk and spinach in Japan. I haven't been able to find the numbers (with background levels), but thought it was worth noting.

I have to wonder how much of that is due to more sensitive instrumentation. TMI was nearly 40 years ago.
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